Process for the manufacture of crank-shafts

ABSTRACT

The present invention relates to a process for the manufacture of crank-shafts, comprising the heating of a cylindrical zone of a blank containing a quantity of material at least equal to that necessary for the forging of a crank-pin and of two webs associated therewith, the die forging (die stamping) of the crank pin and of its two webs, the cooling of the forged part and repetition of the process for zones of the blank adjacent the crank-pin already forged. The invention also relates to a field magnet (or inductor coil) appropriate to the said process.

United States Patent [191 Poncin Dec. 9, 1975 PROCESS FOR THE MANUFACTURE OF 2,669,637 2/1954 Pitt et a1. 29/6 3,684,851 8/1972 Reinke et al 219/1043 CRANK-SHAFIS Inventor: Roger Poncin, Liege, Belgium Assignee: Elphiac S.A., Brussels, Belgium Filed: May 16, 1974 Appl. No.: 470,461

Foreign Application Priority Data May 16, 1973 Belgium 799572 US. Cl 72/342; 29/6 Int. Cl. B21K 1/08 Field of Search 29/6; 72/342; 219/1043 References Cited UNITED STATES PATENTS Primary Examiner-Lowell A. Larson Attorney, Agent, or Firm Raymond A. Robic; Peter G. Mack; Arthur Schwartz [57] ABSTRACT The present invention relates to a process for the manufacture of crank-shafts, comprising the heating of a cylindrical zone of a blank containing a quantity of material at least equal to that necessary for the forging of a crank-pin and of two webs associated therewith, the die forging (die stamping) of the crank pin and of its two webs, the cooling of the forged part and repetition of the process for zones of the blank adjacent the crank-pin already forged. The invention also relates to a field magnet (0r inductor coil) appropriate to the said process.

3 Claims, 1 Drawing Figure U.S. Patent Dec. 9 1975 3,924,439

PROCESS FOR THE MANUFACTURE OF CRANK-SHAFTS It is the object of the invention to limit to the strict minimum the length of the heated zone of the blank which is to be forged, in order to reduce the length of the blank within which the mechanical strength breaks down. It is a second object of the invention to achieve maximum economy with regard to heating energy.

To this end, the process according to the invention is characterised in that the selective heating of a cylindrical portion of the blank takes place in an inductor (or field magnet) comprising a main inductor coil closely surrounding the cylindrical portion of the blank contiguous to a web which has already been forged and having tightly wound turns at the web side and looser turns at the opposite side, and an auxiliary, large-diameter field magnet (or inductor) coaxial with the main field magnet (or inductor) and adapted to surround a forged web presented at an optional angle, and in that the said two main and auxiliary inductors are energised in phase.

The invention is explained hereinbelow with reference to an example of embodiment referring to the accompanying drawing.

The single FIGURE of the drawing shows a section taken through an inductor heating a zone of a premachined cylindrical portion of a blank.

A blank comprising a portion which has already been forged and which is constituted by a crank pin 1 and two webs 2 associated therewith and by a pre-machined cylindrical portion 3 is surrounded by an inductor comprising a main inductor coil 4 and an auxiliary inductor coil 5. The main inductor coil 4 closely surrounds the cylindrical portion 3 of the blank. The auxiliary inductor 5 is co-axial relative to the main inductor 4 and its internal diameter is sufficiently large to surround a web 2 which has already been forged and which is presented at an optional angle.

The main inductor comprises a portion 6 in which the turns are wound more closely and a portion 7 in which the turns are looser. In the present case, the length of the portion 6 is approximately half the diameter of the cylindrical portion 3 of the blank. If, in the portion 7, the number of turns or convolutions per unit length is 1, its density may be for example 1.25 turns per unit length in the portion 6, in order to obtain advantageous conditions; that data given here may vary within relatively wide limits, for example fl%. The portion 6 of the main inductor 4 is located at the side of the web 2 which has already been forged. It is the object thereof to re-inforce the field at the end of the main inductor. The auxiliary inductor has the same object. It is thus necessary to energise or feed the two inductors 4 and 5 in phase. The inductor S-also heats the web 2, but since this web must not be brought to an excessive temperature, energisation or feeding of the inductor 5 is controlled independently of that of the inductor 4. If, for

example, the two inductors 4 and 5 are cut in simultaneously, the inductor 5 is cut out prior to the inductor 4 so as to achieve distribution of the desired temperature, notably a uniform temperature within narrow limits, in the portion to be forged on either side of the portion premachined to a smaller diameter of the portion 3 of the blank.

The inductors 4 and 5 may be embedded in heatinsulating packings, as known per se, and may be formed with pyrometric observation apertures 8. They may be mounted either to be stationary or, on the contrary, on a displacable carriage or slide.

I claim:

1. A process for the stepwise forging of discrete sections of a crankshaft comprising the steps of:

a. relatively positioning a section of a cylindrical blank and a main induction heating coil by:

l. closely surrounding a portion of said 'section contiguous to a previously forged web of the crankshaft by a first part of said main induction heating coil having closely wound turns;

2. closely surrounding another portion of said section, spaced from said previously forged web by a second part of said main induction heating coil having less closely wound turns than said first part;

b. separately surrounding said previously forged web by an auxiliary induction heating coil, which is discrete from said main induction heating coil, which is of substantially larger diameter than said main induction heating coil, and which is disposed coaxially with respect thereto;

c. energizing said main induction heating coil;-

d. energizing said auxiliary induction heating coil in phase;

e. forging a new crankpin and pair of associated webs from said section;

f. cooling the newly forged section;

g. repeating said positioning, surrounding, energizing, forging and cooling steps.

2. The process of claim 1, wherein said energizing steps are carried out such that said main and auxiliary induction heating coils are energized independently of each other, said auxiliary induction heating coil being energized for a shorter duration than said main induction heating coil.

3. The process of claim 1:

a. wherein the length of said portion surrounded by said first part of said main induction heating coil is approximately half the diameter of said cylindrical blank; and

b. wherein said portion surrounded by said first part of said main induction heating coil is surrounded by coils having a turn density approximately 25% greater than that of the coils surrounding the other portion. 

1. A process for the stepwise forging of discrete sections of a crankshaft comprising the steps of: a. relatively positioning a section of a cylindrical blank and a main induction heating coil by:
 1. closely surrounding a portion of said section contiguous to a previously forged web of the crankshaft by a first part of said main induction heating coil having closely wound turns;
 2. closely surrounding another portion of said section, spaced from said previously forged web by a second part of said main induction heating coil having less closely wound turns than said first part; b. separately surrounding said previously forged web by an auxiliary induction heating coil, which is discrete from said main induction heating coil, which is of substantially larger diameter than said main induction heating coil, and which is disposed coaxially with respect thereto; c. energizing said main induction heating coil; d. energizing said auxiliary induction heating coil in phase; e. forging a new crankpin and pair of associated webs from said section; f. cooling the newly forged section; g. repeating said positioning, surrounding, energizing, forging and cooling steps.
 2. closely surrounding another portion of said section, spaced from said previously forged web by a second part of said main induction heating coil having less closely wound turns than said first part; b. separately surrounding said previously forged web by an auxiliary induction heating coil, which is discrete from said main induction heating coil, which is of substantially larger diameter than said main induction heating coil, and which is disposed coaxially with respect thereto; c. energizing said main induction heating coil; d. energizing said auxiliary induction heating coil in phase; e. forging a new crankpin and pair of associated webs from said section; f. cooling the newly forged section; g. repeating said positioning, surrounding, energizing, forging and cooling steps.
 2. The process of claim 1, wherein said energizing steps are carried out such that said main and auxiliary induction heating coils are energized independently of each other, said auxiliary induction heating coil being energized for a shorter duration than said main induction heating coil.
 3. The process of claim 1: a. wherein the length of said portion surrounded by said first part of said main induction heating coil is approximately half the diameter of said cylindrical blank; and b. wherein said portion surrounded by said first part of said main induction heating coil is surrounded by coils having a turn density approximately 25% greater than that of the coils surrounding the other portion. 